<html>

<head></head>

<body>
    <div class="dropdown">
        <button onclick="myFunction()" class="dropbtn">下拉菜单</button>
        <div id="myDropdown" class="dropdown-content">
            <input type="text" placeholder="Search.." id="myInput" onkeyup="filterFunction()">
            <a href="#about">Google</a>
            <a href="#base">Runoob</a>
            <a href="#blog">Taobao</a>
            <a href="#contact">Wiki</a>
            <a href="#custom">Zhihu</a>
            <a href="#support">Tmall</a>
            <a href="#tools">Weibo</a>
        </div>
    </div>
    <style>
        /* 下拉菜单按钮 */
        .dropbtn {
          background-color: #04AA6D;
          color: white;
          padding: 16px;
          font-size: 16px;
          border: none;
          cursor: pointer;
        }
         
        /* 鼠标移动到下拉菜单按钮到样式*/
        .dropbtn:hover, .dropbtn:focus {
          background-color: #3e8e41;
        }
         
        /* 搜索框 */
        #myInput {
          box-sizing: border-box;
          background-image: url('https://static.runoob.com/images/mix/searchicon.png');
          background-position: 14px 12px;
          background-repeat: no-repeat;
          font-size: 16px;
          padding: 14px 20px 12px 45px;
          border: none;
          border-bottom: 1px solid #ddd;
        }
         
        /* 搜索框获取焦点的样式 */
        #myInput:focus {outline: 3px solid #ddd;}
         
        /* 容器 <div> - 定位下拉菜单 */
        .dropdown {
          position: relative;
          display: inline-block;
        }
         
        /* 下拉菜单内容 (默认隐藏) */
        .dropdown-content {
          display: none;
          position: absolute;
          background-color: #f6f6f6;
          min-width: 230px;
          border: 1px solid #ddd;
          z-index: 1;
        }
         
        /* 下拉菜单链接样式 */
        .dropdown-content a {
          color: black;
          padding: 12px 16px;
          text-decoration: none;
          display: block;
        }
         
        /* 鼠标移动到链接上的样式 */
        .dropdown-content a:hover {background-color: #f1f1f1}
         
        /* 显示下拉菜单 (使用 JS 添加 .dropdown-content 类) */
        .show {display:block;}
    </style>

    <script>
        /* 点击按钮设置下拉菜单的显示与隐藏 */
        function myFunction() {
          document.getElementById("myDropdown").classList.toggle("show");
        }
         
        /* 搜索功能 */
        function filterFunction() {
          var input, filter, ul, li, a, i;
          input = document.getElementById("myInput");
          filter = input.value.toUpperCase();
          div = document.getElementById("myDropdown");
          a = div.getElementsByTagName("a");
          for (i = 0; i < a.length; i++) {
            txtValue = a[i].textContent || a[i].innerText;
            if (txtValue.toUpperCase().indexOf(filter) > -1) {
              a[i].style.display = "";
            } else {
              a[i].style.display = "none";
            }
          }
        }
    </script>
</body>

</html>